1. Field of the Invention
The present invention relates to a sheet remainder detecting device for detecting the remaining amount of sheets in a sheet stack and an image forming apparatus employing such a device.
2. Description of the Related Art
There has been conventionally known a sheet remainder detecting device applied to an image forming apparatus as disclosed in Japanese Unexamined Patent Publication No. H04-358648. This sheet remainder detecting device employs a sheet placing plate constructed to lift as the number of sheets is decreased as the sheets are successively fed from a sheet stack placed thereon. This detecting device further includes a light reflector fixed to the sheet placing plate, a plurality of light emitting elements arranged along a movable range of this light reflector for emitting lights toward the light reflector, and a plurality of light receiving elements provided in correspondence with the respective light emitting elements for receiving the lights reflected by the light reflector.
The remaining amount of the sheets on the sheet placing plate is detected by discriminating based on detection signals outputted from the light receiving elements which light receiving element received the light from which light emitting element via the light reflector. According to such a sheet remainder detecting device, a sheet replenishment timing can be known before the sheets run out, actions such as notification to replenish the sheets can be made beforehand, which is convenient because the prolongation of a sheet run-out state can be prevented.
However, the sheet remainder detecting device of the above publication necessitates a multitude of expensive light emitting elements and light receiving elements, thereby presenting a problem of a high parts cost.